Methods of Preparing a Catalyst

ABSTRACT

A hydrogel comprising water, and a plurality of titanium-silica nanoparticle agglomerates, wherein each titanium-silica nanoparticle agglomerate is an agglomeration of titanium-silica nanoparticles, the agglomerates having an average titanium loading designated x with a coefficient of variation for the average titanium loading of less than about 1.0, wherein a silica content of the hydrogel is of from about 10 wt. % to about 35 wt. % based on a total weight of the hydrogel.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of and claims priority to U.S.patent application Ser. No. 16/990,816 filed Aug. 11, 2020, published asU.S. Patent Application Publication No. 2020/0369803 A1, which is acontinuation-in-part of and claims priority to U.S. patent applicationSer. No. 16/851,611 filed Apr. 17, 2020, which is a continuation of andclaims priority to U.S. patent application Ser. No. 15/847,129, filedDec. 19, 2017, now U.S. Pat. No. 10,654,953 B2, which is anon-provisional of and claims priority to U.S. Provisional PatentApplication No. 62/440,188 filed Dec. 29, 2016, and all entitled“Methods of Preparing a Catalyst,” each of which applications isincorporated by reference herein in its entirety.

TECHNICAL FIELD

The present disclosure relates to catalyst compositions. Morespecifically, the present disclosure relates to methods of preparingolefin polymerization catalyst compositions.

BACKGROUND

Enhancements in preparation methods for olefin polymerization catalystscan reduce the costs associated with catalyst production and improveprocess economics. Thus, there is an ongoing need to develop new methodsof preparing olefin polymerization catalysts.

SUMMARY

Disclosed herein is a method of preparing a catalyst support comprisingcontacting an acid-soluble titanium-containing compound with an acid toform a first mixture; contacting the first mixture with an alkali metalsilicate to form a hydrogel which has a silica content of from about 18wt. % to about 35 wt. % based on the total weight of the hydrogel;contacting the hydrogel with an alkaline solution to form an agedhydrogel; washing the aged hydrogel to form a washed hydrogel; anddrying the washed hydrogel to produce a titanium-containing-silicasupport wherein the support has a pore volume equal to or greater thanabout 1.4 cm³/g.

Also disclosed herein is a method of preparing a catalyst comprisingcontacting an acid-soluble titanium-containing compound with an acid toform a first mixture; contacting the first mixture with an alkali metalsilicate to form a hydrogel which has a silica content of from about 18wt. % to about 35 wt. % based on the total weight of the hydrogel;contacting the hydrogel with an alkaline solution to form an agedhydrogel; washing the aged hydrogel to form a washed hydrogel; anddrying the washed hydrogel to produce a titanium-containing-silicasupport; wherein a chromium compound is included in the method to form achrominated-titanium-containing silica, either through cogelation of thehydrogel in the presence of a chromium-containing compound or contactingthe titanium-containing-support with a chromium-containing compound andwherein the support has a pore volume equal to or greater than about 1.4cm³/g.

Also disclosed herein is a method of preparing a catalyst comprisingcontacting an acid-soluble titanium-containing compound with an acid toform a first mixture; contacting the first mixture with an alkali metalsilicate to form a hydrogel which has a silica content of from about 18wt. % to about 35 wt. % based on the total weight of the hydrogel;contacting the hydrogel with an alkaline solution to form an agedhydrogel; washing the aged hydrogel to form a washed hydrogel; dryingthe washed hydrogel to produce a titanium-containing-silica support; andimpregnating the titanium-containing-support with a chromium-containingcompound to form a chrominated-titanium-containing silica wherein thesupport has a pore volume equal to or greater than about 1.4 cm³/g.

Also disclosed herein is a method of preparing a catalyst comprisingcontacting an acid-soluble titanium-containing compound with an acid toform a first mixture; contacting the first mixture with an alkali metalsilicate to form a hydrogel which has a silica content of from about 18wt. % to about 35 wt. % based on the total weight of the hydrogel;contacting the hydrogel with an alkaline solution to form an agedhydrogel; washing the aged hydrogel to form a washed hydrogel; and spraydrying the washed hydrogel in the presence of a chromium-containingcompound to produce a chrominated-titanium-containing silica wherein thesupport has a pore volume equal to or greater than about 1.4 cm³/g.

Also disclosed herein is a method of preparing a catalyst comprisingcontacting an acid-soluble titanium-containing compound and achromium-containing compound with an acid to form a first mixture;contacting the first mixture with an alkali metal silicate to form ahydrogel which has a silica content of from about 18 wt. % to about 30wt. % based on the total weight of the hydrogel; contacting the hydrogelwith an alkaline solution to form an aged hydrogel; washing the agedhydrogel to form a washed hydrogel; and drying the washed hydrogel toform a chrominated-titanium-containing silica wherein the support has apore volume equal to or greater than about 1.4 cm³/g.

Also disclosed herein is a hydrogel comprising water, and a plurality oftitanium-silica nanoparticle agglomerates, wherein each titanium-silicananoparticle agglomerate is an agglomeration of titanium-silicananoparticles, the agglomerates having an average titanium loadingdesignated x with a coefficient of variation for the average titaniumloading of less than about 1.0, wherein a silica content of the hydrogelis of from about 10 wt. % to about 35 wt. % based on a total weight ofthe hydrogel.

BRIEF DESCRIPTION OF DRAWINGS

For a detailed description of the preferred embodiments of the disclosedprocesses and systems, reference will now be made to the accompanyingdrawings in which:

FIGS. 1A and 1B are scanning electron microscopy images for the samplesfrom Example 2.

FIGS. 2A, 2B and 2C are scanning electron microscopy images for thesamples from Example 2.

FIG. 3 depicts the particle size distributions of samples from Example2.

FIG. 4 is a schematic representation of the Auger process.

DETAILED DESCRIPTION

It should be understood at the outset that although an illustrativeimplementation of one or more aspects are provided below, the disclosedsystems and/or methods may be implemented using any number oftechniques, whether currently known or in existence. The disclosureshould in no way be limited to the illustrative implementations,drawings, and techniques illustrated below, including the exemplarydesigns and implementations illustrated and described herein, but may bemodified within the scope of the appended claims along with their fullscope of equivalents.

Disclosed herein are methods for the preparation of catalysts andcatalyst supports. In an aspect, the catalyst support is asilica-titania (Si—Ti) support which is used to produce a polymerizationcatalyst such as a chromium-supported catalyst (Cr/Si—Ti). In an aspect,the present disclosure advantageously affords formation of asilica-titania hydrogel in a substantially aqueous medium duringpreparation of the chromium-supported catalyst. Herein such catalystsare designated hydrogel-derived aqueously titanated catalysts (HATC).

As described in detail herein, a method of the present disclosurecomprises formation of a silica hydrogel support in the presence of anacid-soluble titanium-containing compound. A titanium-containingcompound suitable for use in the present disclosure may be anyacid-soluble compound able to release a tetravalent titanium species, atrivalent titanium species or a titanium species that can readilyconvert to tetravalent titanium into solution. In an aspect, theacid-soluble titanium-containing compound comprises trivalent titanium,tetravalent titanium, titania, or combinations thereof. For example, theacid-soluble titanium-containing compound can comprise tetravalenttitanium such as TiCl₄, TiOSO₄, TiBr₄, TiOCl₂, TiOBr₂, TiO₂,TiO(oxylate)₂, or combinations thereof. Alternatively, the acid-solubletitanium-containing compound can comprise trivalent titanium such asTi₂(SO₄)₃, Ti(OAc)₃, Ti(oxylate)₃, Ti(NO₃)₃, or combinations thereof.

As described in detail herein, chromium may be introduced to the silicasupport during cogellation of the hydrogel or via contact of the supportwith a chromium-containing compound. The chromium-containing compoundmay be one or more compounds comprising chromium in the hexavalentoxidation state (hereinafter Cr(VI)) or comprising a material suitablefor conversion to Cr(VI). In an aspect, the chromium-containing compoundcomprises a water-soluble chromium compound; alternatively thechromium-containing compound comprises a hydrocarbon-soluble chromiumcompound.

The chromium-containing compound may be a chromium (II) compound,chromium (III) compound, or combinations thereof. Suitable chromium(III) compounds include, but are not limited to, chromium carboxylates,chromium naphthenates, chromium halides, chromium pyrrolides, chromiumbenzoates, chromium dionates, chromium nitrates, chromium sulfates, orcombinations thereof. Specific chromium (III) compounds include, but arenot limited to, chromium (III) isooctanoate, chromium (III)2,2,6,6-tetramethylheptanedionate, chromium (III) naphthenate, chromium(III) chloride, chromium (III) tris(2-ethylhexanoate), chromic fluoride,chromium (III) oxy-2-ethylhexanoate, chromium (III)dichloroethylhexanoate, chromium (III) acetylacetonate, chromium (III)acetate, chromium (III) butyrate, chromium (III) neopentanoate, chromium(III) laurate, chromium (III) sulfate, chromium (III) oxalate, chromium(III) benzoate, chromium (III) pyrrolide(s), chromium (III) perchlorate,chromium (III) chlorate, or combinations thereof. Suitable chromium (II)compounds include, but are not limited to, chromous fluoride, chromouschloride, chromous bromide, chromous iodide, chromium (II)bis(2-ethylhexanoate), chromium (II) acetate, chromium (II) butyrate,chromium (II) neopentanoate, chromium (II) laurate, chromium (II)stearate, chromium (II) oxalate, chromium (II) benzoate, chromium (II)pyrrolide(s), chromous sulfate, or combinations thereof. Examples ofother suitable chromium-containing compounds include tertiary butylchromate in a hydrocarbon liquid; chromium trioxide in water; chromiumacetate in water; chromium nitrate in alcohol; zerovalent organochromiumcompounds such as pi bonded chromium complexes, for example, dicumenechromium and dibenzene chromium; or combinations thereof. Pi bondedchromium complexes are described in U.S. Pat. No. 3,976,632, which isincorporated by reference herein in its entirety.

In an aspect of the present disclosure, a method of preparing a HATCcomprises contacting an acid-soluble titanium-containing compound of thetype disclosed herein (which may be in the form of an aqueous solution)with an acid (which may be in the form of an aqueous solution) to forman acidic titanium-containing aqueous solution. The acid may be any acidcapable of solubilizing, and being present in an amount effective todissolve, the acid-soluble titanium compound and compatible with theother components of the HATC. In an aspect, the acid is a mineral acidsuch as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid,phosphoric acid, perchloric acid, sulfamic acid, or any combinationthereof. The acidic titanium-containing solution may have titaniumpresent in an amount of from about 0.1 weight percent (wt. %) to about10 wt. % based on the weight of the solution, alternatively from about0.25 wt. % to about 8 wt. %, or alternatively from about 0.5 wt. % toabout 6 wt. %.

A method of the present disclosure may further comprise contacting theacidic titanium-containing aqueous solution with an alkali metalsilicate (which may be in the form of an aqueous solution) to form atitanium-containing silica hydrogel. Herein a “hydrogel” refers to anetwork of silicate chains that are insoluble in water and may be foundas a colloidal gel in which water was the dispersion medium prior togellation. The alkali metal silicate may be any compound capable offorming a hydrogel when contacted with the acidic titanium-containingsolution and compatible with the other components of the HATC. In anaspect, the alkali metal silicate is sodium silicate (e.g., an aqueoussodium silicate solution). Other suitable alkali metal silicates includeaqueous solutions of potassium silicate or lithium silicate. Colloidalsilicas, made commercially by ion exchanging the alkali metal out canalso be used.

In an aspect, the alkali metal silicate is added to the acidictitanium-containing solution so that the pH of the solution is raisedand at some point the solution sets up into a hydrogel. The pH of thesolution at gelation can be from about 1.5 to about 7, alternativelyfrom about 2 to about 5, or alternatively from about 2 to about 4.Alternatively, a base such as NaOH or NH₄OH can also be added to raisethe pH. For example, if a colloidal silicate solution is used as thesilica source, then base can be added to neutralize the colloidalsolution. Alternatively, an alkali metal silicate solution can be addedto the titanium-containing solution to partially neutralize the acidity,and base can then be added to cause gelation.

In an aspect, the alkali metal silicate is a concentrated aqueoussolution so that the resulting hydrogel contains a high concentration ofsilica. After gelation and washing to remove salts, the hydrogel maycontain from about 10 wt. % to about 35 wt. % silica, alternatively fromabout 15 wt. % to about 30 wt. %, alternatively from about 18% to about30%, alternatively from about 20 wt. % to about 30 wt. % silica, oralternatively from about 22 wt. % to about 28 wt. % silica. Thetitanium-containing silica hydrogel may be formed using a continuousprocess, also referred to as an acid-set continuous gelation process,wherein the solution pH of the combined aqueous mixture comprising theacidic titanium-containing solution and alkali metal silicate is equalto or less than about 6, alternatively equal to or less than about 5,alternatively equal to or less than about 4, alternatively equal to orless than about 3, or alternatively from about 3 to about 6. Forexample, an acidic titanium-containing aqueous solution can be formed bycombining an aqueous acid (e.g., sulfuric acid) and an aqueous titaniumcompound (e.g., titanyl sulfate) to form an acidic titanium-containingaqueous solution, and the acidic titanium-containing aqueous solutioncan be continuously combined with an alkali metal silicate aqueoussolution (e.g., a concentrated sodium silicate aqueous solution) in arapid mixer, from which a hydrosol is emitted onto a vat or continuousconveyor belt where it gels rapidly (e.g., within a few seconds) to formthe titanium-containing silica hydrogel.

Herein the pore volume of a hydrogel refers to the grams of pore waterin the pores of the hydrogel, per g of silica. In an aspect, a hydrogelof the present disclosure is characterized by a pore volume ranging fromabout 1.9 g/g to about 9 g/g, alternatively from about 2.3 g/g to about5.6 g/g or alternatively from about 2.3 g/g to about 4.0 g/g, oralternatively from about 1.9 g/g to about 4.0 g/g.

In a method of the present disclosure, the titanium-containing silicahydrogel may then be alkaline aged to form an aged titanium-containingsilica hydrogel. Such alkaline aging treatment is also known as “Oswaldripening”. It is a way of reinforcing the silica network, because silicais dissolved from areas of low surface energy and then re-deposited intoareas of higher surface energy, such as into the crevices created by thecontacting of neighboring silica primary particles. In this way theintricate substructure of the gel, which is created by the combinationof billions of individual primary silica particles loosely attached, islost. Instead these smaller particles become fused together into a morehomogeneous mass. The surface area is thus lowered, the pores are openedup, and the entire framework become much stronger.

Herein alkaline ageing of the titanium-containing silica hydrogel may becarried out by contacting the titanium-containing silica hydrogel withan alkaline aqueous solution comprising one or more basic compounds(e.g., bases, buffer) having a pH of from about 8 to about 13,alternatively from about 9 to about 12, or alternatively from about 9 toabout 10 at a temperature of from about 60° C. to about 90° C.,alternatively from about 70° C. to about 85° C., or alternatively atabout 80° C. The alkaline aqueous solution may be comprised of anycomponents which provide a solution pH in the disclosed ranges and arecompatible with the other components of the composition. For example,the alkaline aqueous solution may comprise ammonium hydroxide, potassiumhydroxide, sodium hydroxide, trialkylammonium hydroxide, sodiummetasilicate, tetra-alkyl ammonium hydroxide or combinations thereof.Alkaline aging of the titanium-containing silica hydrogel may be carriedout for a time period sufficient to lower the surface area of the silicasupport to less than about 60% of the original value, alternatively toless than about 50% of the original value, alternatively to less thanabout 40% of the original value, or alternatively to less than about 35%of the original value of the surface area of an otherwise similarmaterial that has not been alkaline aged. In an aspect, alkaline agingof the titanium-containing silica hydrogel is carried out for a timeperiod of from about 1 hour to about 24 hours, or from about 2 hours toabout 10 hours, or from about 3 hours to about 6 hours. Hereinafter thealkaline ageing parameters disclosed (e.g., compounds, pH, time,temperature, etc.) are collectively termed the standard alkaline ageingconditions.

A method of preparing a HATC of the type disclosed herein may furthercomprise washing the aged titanium-containing silica hydrogel with waterand/or with any suitable compound such as ammonium salt (e.g., ammoniumnitrate, etc.) or diluted acid to produce a washed titanium-containingsilica hydrogel. In an aspect, the aged titanium-containing silicahydrogel is washed to reduce the alkali metal content of the silicahydrogel to some user or process desired level. Consequently, washing ofthe aged titanium-containing silica hydrogel may be carried out severaltimes or until a user-desired result is achieved.

In an aspect, the method further comprises drying the washedtitanium-containing silica hydrogel to form a dried hydrogel. Drying thewashed titanium-containing silica hydrogel may be carried out to removeall or a portion of the aqueous solution from the composition. Forexample, the composition may be dried using standard techniques such asthermal treatment, spray drying, tray drying, oven drying, flash drying,or first contacting with a volatile liquid organic solvent to replacethe pore water of the hydrogel with the organic liquid of lower surfacetension. Examples of volatile liquid organic solvents include withoutlimitation methyl isobutylketone, ethyl acetate, sec-butyl alcohol,n-propyl alcohol, butyraldehyde, diisobutyl ether, isopropyl acetate,3-methyl-1-butanol, 1-pentanol, 2-pentanol, 1-hexanol or combinationsthereof.

In an aspect, the washed titanium-containing silica hydrogel is dried ina temperature range of from about 25° C. to about 300° C., alternativelyfrom about 50° C. to about 200° C., or alternatively from about 80° C.to about 150° C. and for a time of from about 0.01 min to about 10hours, alternatively from about 0.2 min to about 5 hours, oralternatively from about 30 min to about 1 hour. Alternatively, thewashed titanium-containing silica hydrogel can be dried from 1 sec to 10sec. Hereinafter the drying parameters disclosed (e.g., compounds, time,temperature, etc.) may be collectively termed the standard dryingconditions. Drying of the washed titanium-containing silica hydrogel mayconvert the material to a titanium-containing silica xerogel and theresultant alkaline-aged, washed, and dried titanium-containing silicaxerogel is hereinafter termed a titanium-containing-silica support.

In an aspect, a method of the present disclosure further comprisescontacting of the titanium-containing-silica support with achromium-containing compound to form a chrominated-titanium-containingsilica support, or more simply a metallated support. Thechromium-containing compound may be contacted with thetitanium-containing-silica support using any suitable methodology suchas ion-exchange, incipient wetness, spray drying, pore fill, aqueousimpregnation, organic solvent impregnation, melt coating, or the like.

In an aspect of the present disclosure the metallated support isoptionally dried to remove solvent introduced by the addition of thechromium-containing compound. Drying of the metallated support may becarried out at temperatures ranging from about 25° C. to about 300° C.,alternatively from about 50° C. to about 200° C., or alternatively fromabout 80° C. to about 150° C. to form a dried metallated support. Insome aspects, the metallated support (or dried metallated support) maybe activated via calcination by heating in an oxidizing environment toproduce the HATC. For example, the metallated support (or driedmetallated support) may be calcined in the presence of air at atemperature in the range of from about 400° C. to about 1,000° C.,alternatively from about 500° C. to about 850° C. and for a time of fromabout 1 min to about 10 hours, alternatively from about 20 min to about5 hours, alternatively from about 1 hour to about 3 hours to produce theHATC. Hereinafter the calcination parameters disclosed (e.g., time,temperature, etc.) may be collectively termed the standard calcinationconditions.

In an aspect, the method of preparation of a HATC of the type disclosedherein may comprise contacting of the chromium-containing compound withone or more of the other catalyst components at any time during the HATCpreparation process. In an aspect, the chromium-containing compound maybe added via tergelation of the hydrogel. For example, thechromium-containing compound may be simultaneously contacted with anacidic titanium-containing solution and an alkali metal silicate (e.g.,sodium silicate) to form a metallated support. In such aspects, themetallated support may be subsequently alkaline aged under standardalkaline ageing conditions to form an aged metallated support. The agedmetallated support may be subsequently washed and dried under standardwashing and drying conditions to form a dried metallated support. Themethod may further comprise calcining the dried metallated support understandard calcination conditions to form the HATC. In an alternativeaspect, the chromium may be added prior to the aging step, as an aqueoussolution of a chromium compound, such as Cr(NO₃)₃, Cr₂(SO₄)₃, CrO₃,Cr(OAc)₃, etc.

In an alternative aspect, the chromium-containing compound may becontacted with the aged titanium-containing silica hydrogel to form anaged metallated hydrogel. The aged metallated hydrogel may be washed,dried and then calcined all under the disclosed standard conditions forsuch processes to form a HATC.

In an alternative aspect, the chromium-containing compound may becontacted with the washed titanium-containing silica hydrogel to form awashed metallated silica hydrogel which can be dried and then calcined,all under the disclosed standard conditions for such processes, to forman HATC.

In an alternative aspect, the chromium-containing compound may becontacted concurrent with drying the washed hydrogel to form a driedmetallated hydrogel. For example, the chromium-containing compound canbe added to the washed hydrogel and subsequently emitted through one ormore spray dryer nozzles such that chromium is present in the resultantdried metallated hydrogel. The dried metallated hydrogel may be thencalcined under the disclosed standard conditions for such processes toform a HATC.

In an alternative aspect, the chromium-containing compound may becontacted with the dried silica-titania support. This can be done byimpregnating the support with an aqueous or organic solution ofchromium, such as chromium (III) acetate dissolved in isopropanol.Alternatively, the chromium-containing compound may be contacted withthe dried silica-titania support by treating the dried support with avapor containing chromium, such as chromium (III) 2,4-pentanedionate,which sublimes during the calcination step.

In an alternative aspect, the chromium may be added after thesilica-support has been calcined. Typically this is done by treatmentwith a non-protic organochromium compound, such as dicumene Cr(0) intoluene solution, or chromium (III) 2,4-pentanedionate in toluene or asa vapor, for example using CrO₂Cl₂ in hydrocarbon solution, or bytreatment with Cr(CO)₆ vapor. The catalyst can be given an additionaldrying step in dry air at a temperature between 100° C. and 600° C. whenCr is deposited in this fashion.

In an aspect of the present disclosure, the HATC has a silica-titaniasupport that possesses a surface area in the range of from about 100m²/gram to about 1000 m²/gram, alternatively from about 400 m²/gram toabout 1000 m²/gram, alternatively from about 250 m²/gram to about 700m²/gram, alternatively from about 250 m²/gram to about 600 m²/gram, oralternatively greater than about 250 m²/gram. The dried silica-titaniasupport may be further characterized by a pore volume of greater thanabout 1.0 cm³/gram, alternatively greater than about 1.4 cm³/gram,alternatively greater than about 1.5 cm³/gram, or alternatively greaterthan about 1.7 cm³/gram. In an aspect of the present disclosure, thesilica-titania support is characterized by a pore volume ranging fromabout 1.0 cm³/gram to about 2.5 cm³/gram. The silica-titania support maybe further characterized by an average particle size of from about 10microns to about 500 microns, alternatively about 25 microns to about300 microns, or alternatively about 40 microns to about 150 microns.Generally, the average pore size of the silica-titania support rangesfrom about 10 Angstroms to about 1000 Angstroms. In one aspect of thepresent disclosure, the average pore size of the silica-titania supportmaterial is in the range of from about 50 Angstroms to about 500Angstroms, while in yet another aspect of the present disclosure theaverage pore size ranges from about 75 Angstroms to about 350 Angstroms.The silica-titania support may contain greater than about 50 percent (%)silica, alternatively greater than about 80% silica, or alternativelygreater than about 95% silica by weight of the silica-titania support.

In an aspect of the present disclosure, the HATC has titanium present inan amount of from about 0.01 wt. % to about 10 wt. % titanium by weightof the HATC, alternatively from about 0.5 wt. % to about 7 wt. %,alternatively from about 1 wt. % to about 5 wt. %, or alternatively fromabout 2 wt. % to about 4 wt. %. In another aspect of the presentdisclosure, the amount of titanium in the HATC may range from about 1wt. % to about 5 wt. %. Herein, the percentage titanium refers to thefinal weight percent titanium associated with the HATC by total weightof the HATC after all processing steps (e.g., after final activation viacalcination).

In another aspect of this disclosure the average titania wt % Ti can beless than about 10 wt. % Ti, alternatively less than about 8 wt. % Ti,alternatively less than about 6 wt. % Ti, alternatively less than about5 wt. % Ti, alternatively less than about 4 wt. % Ti or alternativelyless than about 3.5 wt. % Ti.

In still another aspect of this disclosure the titanium loading can bedefined as titanium atoms per square nanometer (sqnm) of surface area ofthe silica-titania support. In an aspect, the titanium loading is fromabout 1 to less than about 4 titanium atoms/sqnm, alternatively lessthan about 4 titanium atoms/sqnm, alternatively less than about 3titanium atoms/sqnm, alternatively less than about 2 titaniumatoms/sqnm, alternatively less than about 1.5 titanium atoms/sqnm,alternatively less than about 1.2 titanium atoms/sqnm, or alternativelyless than about 1.0 titanium atoms/sqnm.

In an aspect of the present disclosure, the HATC has chromium present inan amount of about 0.01 wt. % to about 10 wt. %, alternatively fromabout 0.5 wt. % to about 5 wt. %, alternatively from about 1 wt. % toabout 4 wt. %, or alternatively from about 2 wt. % to about 4 wt. %. Inanother aspect of the present disclosure, the amount of chromium presentin the HATC may range from about 1 wt. % to about 5 wt. %. Herein, thepercentage chromium refers to the final weight percent chromiumassociated with the HATC by total weight of the HATC after allprocessing steps (e.g., after final activation via calcination).

During catalyst production, materials such as highly reactive volatileorganic compounds (HRVOC) may be emitted. HRVOCs play a role in theformation of ozone in ozone nonattainment areas, i.e., areas that do notmeet the Environmental Protection Agency's air quality standards forground-level ozone. In an aspect of the present disclosure, an olefinpolymerization catalyst prepared as disclosed herein (i.e., HATC)results in a reduction in the level of HRVOCs produced during the olefinpolymerization catalyst preparation. For example, the HRVOCs maycomprise hydrocarbons, aromatic compounds, alcohols, ketones, orcombinations thereof. In an aspect of the present disclosure, the HRVOCscomprise alkenes, alternatively propylene, butene, ethylene, orcombinations thereof. In an aspect, emissions of HRVOCs from olefinpolymerization catalysts prepared as disclosed herein (i.e., HATCs) arefrom about 0 wt. % to about 1 wt. % based on the total weight of thesilica, alternatively less than about 1 wt. %, alternatively less thanabout 0.5 wt. %, or alternatively less than about 0.1 wt. %. In anaspect of the present disclosure, the HRVOC emissions of olefincompounds such as propylene, ethylene, butenes, and other hydrocarbonsare less than about 0.5 wt. %, alternatively less than about 0.25 wt. %,or alternatively less than about 0.1 wt. % based on the total weight ofsilica in the HATC.

Alternatively, another way of gauging potential emissions is by thetotal amount of carbon left on the catalyst after drying. Catalysts madeaccording to the precepts disclosed herein are noteworthy in that thesematerials have little or no residual carbon. These catalysts (i.e.,HATCs) may be characterized as having less than about 1 wt. % carbonleft on the support after drying, or alternatively less than about 0.7wt. %, alternatively less than about 0.5 wt. %, alternatively less thanabout 0.3 wt. %, or alternatively less than about 0.1 wt % residualcarbon based on the total weight of carbon present in the catalyst priorto drying.

Carbon is also important because it determines the amount of heatrelease, or exotherm, during the calcination step, where the carbon isburned. Such exotherms can damage the catalyst if the temperature spikeis too high when the carbon starts to burn. The catalysts of thisdisclosure are noteworthy in having very little exotherm duringactivation. HATCs of the type disclosed herein can be characterized ashaving an exotherm, or temperature spike upon ignition, of less thanabout 200° C. Alternatively the exotherm for HATCs of the type disclosedherein are less than about 100° C., alternatively less than about 50°C., or alternatively less than about 10° C.

The catalysts of the present disclosure (i.e., HATCs) are suitable foruse in any olefin polymerization method, using various types ofpolymerization reactors. As used herein, “polymerization reactor”includes any reactor capable of polymerizing olefin monomers to producehomopolymers and/or copolymers. Homopolymers and/or copolymers producedin the reactor may be referred to as resin and/or polymers. The varioustypes of reactors include, but are not limited to those that may bereferred to as batch, slurry, gas-phase, solution, high pressure,tubular, autoclave, or other reactor and/or reactors. Gas phase reactorsmay comprise fluidized bed reactors or staged horizontal reactors.Slurry reactors may comprise vertical and/or horizontal loops. Highpressure reactors may comprise autoclave and/or tubular reactors.Reactor types may include batch and/or continuous processes. Continuousprocesses may use intermittent and/or continuous product discharge ortransfer. Processes may also include partial or full direct recycle ofun-reacted monomer, un-reacted comonomer, catalyst and/or co-catalysts,diluents, and/or other materials of the polymerization process.

Polymerization reactor systems of the present disclosure may compriseone type of reactor in a system or multiple reactors of the same ordifferent type, operated in any suitable configuration. Production ofpolymers in multiple reactors may include several stages in at least twoseparate polymerization reactors interconnected by a transfer systemmaking it possible to transfer the polymers resulting from the firstpolymerization reactor into the second reactor. Alternatively,polymerization in multiple reactors may include the transfer, eithermanual or automatic, of polymer from one reactor to subsequent reactoror reactors for additional polymerization. Alternatively, multi-stage ormulti-step polymerization may take place in a single reactor, whereinthe conditions are changed such that a different polymerization reactiontakes place.

The desired polymerization conditions in one of the reactors may be thesame as or different from the operating conditions of any other reactorsinvolved in the overall process of producing the polymer of the presentdisclosure. Multiple reactor systems may include any combinationincluding, but not limited to multiple loop reactors, multiple gas phasereactors, a combination of loop and gas phase reactors, multiple highpressure reactors or a combination of high pressure with loop and/or gasreactors. The multiple reactors may be operated in series or inparallel. In an aspect, any arrangement and/or any combination ofreactors may be employed to produce the polymer of the presentdisclosure.

According to one aspect, the polymerization reactor system may compriseat least one loop slurry reactor. Such reactors are commonplace, and maycomprise vertical or horizontal loops. Monomer, diluent, catalystsystem, and optionally any comonomer may be continuously fed to a loopslurry reactor, where polymerization occurs. Generally, continuousprocesses may comprise the continuous introduction of a monomer, acatalyst, and/or a diluent into a polymerization reactor and thecontinuous removal from this reactor of a suspension comprising polymerparticles and the diluent. Reactor effluent may be flashed to remove theliquids that comprise the diluent from the solid polymer, monomer and/orcomonomer. Various technologies may be used for this separation stepincluding but not limited to, flashing that may include any combinationof heat addition and pressure reduction; separation by cyclonic actionin either a cyclone or hydrocyclone; separation by centrifugation; orother appropriate method of separation.

Typical slurry polymerization processes (also known as particle-formprocesses) are disclosed in U.S. Pat. Nos. 3,248,179, 4,501,885,5,565,175, 5,575,979, 6,239,235, 6,262,191 and 6,833,415, for example;each of which are herein incorporated by reference in their entirety.

Suitable diluents used in slurry polymerization include, but are notlimited to, the monomer being polymerized and hydrocarbons that areliquids under reaction conditions. Examples of suitable diluentsinclude, but are not limited to, hydrocarbons such as propane,cyclohexane, isobutane, n-butane, n-pentane, isopentane, neopentane, andn-hexane. Some loop polymerization reactions can occur under bulkconditions where no diluent is used. An example is polymerization ofpropylene monomer as disclosed in U.S. Pat. No. 5,455,314, which isincorporated by reference herein in its entirety.

According to yet another aspect, the polymerization reactor may compriseat least one gas phase reactor. Such systems may employ a continuousrecycle stream containing one or more monomers continuously cycledthrough a fluidized bed in the presence of the catalyst underpolymerization conditions. A recycle stream may be withdrawn from thefluidized bed and recycled back into the reactor. Simultaneously,polymer product may be withdrawn from the reactor and new or freshmonomer may be added to replace the polymerized monomer. Such gas phasereactors may comprise a process for multi-step gas-phase polymerizationof olefins, in which olefins are polymerized in the gaseous phase in atleast two independent gas-phase polymerization zones while feeding acatalyst-containing polymer formed in a first polymerization zone to asecond polymerization zone. One type of gas phase reactor is disclosedin U.S. Pat. Nos. 4,588,790, 5,352,749, and 5,436,304, each of which isincorporated by reference in its entirety herein.

According to still another aspect, a high pressure polymerizationreactor may comprise a tubular reactor or an autoclave reactor. Tubularreactors may have several zones where fresh monomer, initiators, orcatalysts are added. Monomer may be entrained in an inert gaseous streamand introduced at one zone of the reactor. Initiators, catalysts, and/orcatalyst components may be entrained in a gaseous stream and introducedat another zone of the reactor. The gas streams may be intermixed forpolymerization. Heat and pressure may be employed appropriately toobtain optimal polymerization reaction conditions.

According to yet another aspect, the polymerization reactor may comprisea solution polymerization reactor wherein the monomer is contacted withthe catalyst composition by suitable stirring or other means. A carriercomprising an organic diluent or excess monomer may be employed. Ifdesired, the monomer may be brought in the vapor phase into contact withthe catalytic reaction product, in the presence or absence of liquidmaterial. The polymerization zone is maintained at temperatures andpressures that will result in the formation of a solution of the polymerin a reaction medium. Agitation may be employed to obtain bettertemperature control and to maintain uniform polymerization mixturesthroughout the polymerization zone. Adequate means are utilized fordissipating the exothermic heat of polymerization.

Polymerization reactors suitable for the present disclosure may furthercomprise any combination of at least one raw material feed system, atleast one feed system for catalyst or catalyst components, and/or atleast one polymer recovery system. Suitable reactor systems for thepresent invention may further comprise systems for feedstockpurification, catalyst storage and preparation, extrusion, reactorcooling, polymer recovery, fractionation, recycle, storage, loadout,laboratory analysis, and process control.

Conditions that are controlled for polymerization efficiency and toprovide polymer properties include, but are not limited to temperature,pressure, type and quantity of catalyst or co-catalyst, and theconcentrations of various reactants. Polymerization temperature canaffect catalyst productivity, polymer molecular weight and molecularweight distribution. Suitable polymerization temperatures may be anytemperature below the de-polymerization temperature, according to theGibbs Free Energy Equation. Typically, this includes from about 60° C.to about 280° C., for example, and/or from about 70° C. to about 110°C., depending upon the type of polymerization reactor and/orpolymerization process.

Suitable pressures will also vary according to the reactor andpolymerization process. The pressure for liquid phase polymerization ina loop reactor is typically less than 1000 psig (6.9 MPa). Pressure forgas phase polymerization is usually at about 200 psig (1.4 MPa)-500 psig(3.45 MPa). High pressure polymerization in tubular or autoclavereactors is generally run at about 20,000 psig (138 MPa); to 75,000 psig(518 MPa). Polymerization reactors can also be operated in asupercritical region occurring at generally higher temperatures andpressures. Operation above the critical point of a pressure/temperaturediagram (supercritical phase) may offer advantages.

The concentration of various reactants can be controlled to producepolymers with certain physical and mechanical properties. The proposedend-use product that will be formed by the polymer and the method offorming that product may be varied to determine the desired finalproduct properties. Mechanical properties include, but are not limitedto tensile strength, flexural modulus, impact resistance, creep, stressrelaxation and hardness tests. Physical properties include, but are notlimited to density, molecular weight, molecular weight distribution,melting temperature, glass transition temperature, temperature melt ofcrystallization, density, stereoregularity, crack growth, short chainbranching, long chain branching and rheological measurements.

The concentrations of monomer, co-monomer, hydrogen, co-catalyst,modifiers, and electron donors are generally important in producingspecific polymer properties. Comonomer may be used to control productdensity. Hydrogen may be used to control product molecular weight.Co-catalysts may be used to alkylate, scavenge poisons and/or controlmolecular weight. The concentration of poisons may be minimized, aspoisons may impact the reactions and/or otherwise affect polymer productproperties. Modifiers may be used to control product properties andelectron donors may affect stereoregularity.

Polymers such as polyethylene homopolymers and copolymers of ethylenewith other mono-olefins may be produced in the manner described aboveusing the HATCs prepared as described herein. Polymer resins produced asdisclosed herein may be formed into articles of manufacture or end usearticles using techniques known in the art such as extrusion, blowmolding, injection molding, fiber spinning, thermoforming, and casting.For example, a polymer resin may be extruded into a sheet, which is thenthermoformed into an end use article such as a container, a cup, a tray,a pallet, a toy, or a component of another product. Examples of otherend use articles into which the polymer resins may be formed includepipes, films, bottles, fibers, and so forth. Additional end use articleswould be apparent to those skilled in the art.

The HATCs of the present disclosure may possess an organizationalstructure characterized on the atomic level by a network oftitanium-oxygen-silicon bonds in which these atoms are on the order ofangstroms apart. This network of titanium-oxygen-silicon bonds resultsin the formation of titania-silica nanoparticles. In one aspect, thetitania-silica nanoparticles formed during the preparation of HATCs havean average particle size of about 5 nanometers (nm), alternatively fromabout 2 nm to about 10 nm; alternatively from about 3 nm to about 8 nmor alternatively from about 4 nm to about 7 nm. Throughout thisdisclosure the term “particle size” refers to the diameter of a spherethat has the same volume as that of the particle being described. Thediameter of this sphere can be in nanometers, for nano-particles, ormicrons, for macro-particles. Macro-particles comprise agglomerates ofnano-particles.

HATCs nanoparticles may have a coefficient of variance of equal to orless than about 1, alternatively from about 0.1 to about 0.9 oralternatively from about 0.2 to about 0.9, for the particle size of thetitanium-silica nanoparticles. Herein the coefficient of variance (CV)refers to the ratio of the standard deviation to the mean. As usedherein, distributions with a coefficient of variance of less than 1 areconsidered to be low-variance, whereas those with a CV higher than 1 areconsidered to be high variance.

The titanium-silica nanoparticles of the present disclosure can then beprocessed (gelled, ground and spray-dried, for example) as disclosedherein to form agglomerates of titanium-silica nanoparticles, which arealso called “macroparticles,” having average agglomerate particle sizesof about 100 microns, alternatively from about 40 microns to about 200microns or alternatively from about 50 microns to about 200 microns.

The HATCs of the present disclosure may advantageously catalyze theformation of polymers (e.g., polyethylene) having a narrow molecularweight distribution (MWD) when compared to conventional Ti—Cr/Sicatalysts. For example, polymers prepared using HATCs of the presentdisclosure may have a MWD that is decreased by from about 3 to about 25,alternatively from about 4 to about 20 or alternatively from about 5 toabout 15 when compared to an otherwise similar polymer prepared using aTi—Si catalyst without the formation of a Ti—Si hydrogel.

The polymers (e.g., polyethylene) produced by the catalysts of thisdisclosure (i.e., HATCs) may have a melt index ranging from about 0.01g/10 min to about 100 g/10 min, alternatively from about 0.1 g/10 min toabout 10 g/10 min, alternatively from about 0.15 g/10 min to about 5g/10 min, alternatively from about 0.2 g/10 min to about 3 g/10 min, oralternatively from about 0.25 g/10 min to about 1.5 g/10 min. In anaspect, polymers produced by catalysts of the present disclosure (e.g.,HATCs) may display an HLMI in the range of from about 1 g/10 min toabout 1000 g/10 min, alternatively from about 5 g/10 min to about 500g/10 min, alternatively from about 10 g/10 min to about 100 g/10 min,alternatively from about 15 g/10 min to about 90 g/10 min, oralternatively from about 20 g/10 min to about 80 g/10 min providing aHLMI/MI ratio or shear response ranging from about 30 g/10 min to about500 g/10 min, alternatively from about 40 g/10 min to about 400 g/10min, alternatively from about 45 g/10 min to about 300 g/10 min, oralternatively from about 50 g/10 min to about 200 g/10 min. The MIrepresents the rate of flow of a molten polymer through an orifice of0.0825 inch diameter when subjected to a force of 2,160 grams at 190° C.as determined in accordance with ASTM D1238-82 condition. The HLMIrepresents the rate of flow of a molten polymer through an orifice of0.0825 inch diameter when subjected to a force of 21,600 grams at 190°C. as determined in accordance with ASTM D1238-82 condition F.

The narrow MWD, melt index and branching characteristics of polymers ofthe present disclosure may be attributed to the presently disclosedcatalysts (e.g., HATCs) exhibiting the characteristics of (i) uniformityof catalyst particle size and (ii) uniformity of titanium distribution.

Herein the uniformity of the catalyst macroparticle size or the catalystmacroparticle size distribution can be determined using any suitablemethodology such as laser light scattering or sieving. In an aspect, theHATCs have a macroparticle size distribution of from about 0.1 μm toabout 400 μm, alternatively from about 1 μm to about 350 μm,alternatively from about 5 μm to about 300 μm, or alternatively fromabout 5 μm to about 100 μm.

Herein the uniformity of titanium distribution in the HATC refers to 1)the extent to which titanium is distributed throughout the entire massof the larger macroparticles, and 2) the distribution of Ti betweenmacroparticles of varying size. The distribution of the titanium may bequantified using any suitable methodology. For example, the distributionof titanium may be determined by scanning electron microscopy. In anaspect, HATCs of the present disclosure have titanium distributedthroughout the entirety of the particle such that visualization by SEMresults in the appearance of titanium in greater than about 80% of theentire particle, alternatively greater than about 90%, or alternativelygreater than about 95%.

Herein the titanium distribution may also be assessed as a function ofparticle size. Specifically, the titanium distribution can be determinedon the basis of titanium content as a function of particle size. In suchan aspect. a first group comprising the smallest 10% of particles isestablished, termed S_(s) and a second group comprising the largest 10%of particle sizes is established, termed Si. In an aspect, the ratio oftitanium in S_(s):S_(l) is about 1. Alternatively, the S_(s):S_(l) isfrom about 0.8 to about 1.2, alternatively from about 0.85 to about1.15, alternatively from about 0.9 to about 1.1, or alternatively fromabout 0.95 to about 1.05.

In another aspect, microtoming of the 10% largest particles (Si)indicates that titania content on the outside of the particles (Ti_(o))is approximately equal to that of the center of the particles (Ti_(c)).In other words, HATCs of the present disclosure are characterized by aTi_(o)/Ti_(c) of about 1, alternatively from about 0.8 to about 1.2,alternatively from about 0.85 to about 1.15, alternatively from about0.9 to about 1.1, or alternatively from about 0.95 to about 1.05.Microtoming is an experimental technique which slices sections of asample for microscopic examination, using a light or electronmicroscope.

In an aspect, the uniformity of titanium distribution for the presentlydisclosed catalysts (i.e., HATCs) can be assessed through evaluation ofthe melt index or high load melt index of polymers produced using thecatalysts of the present disclosure. Specifically, polymer samples(e.g., polyethylene) can be prepared using a catalyst consistingessentially of S_(s) particles or essentially of Si particles asdisclosed herein to produce polymer samples termed P_(s) and P_(l)respectively. In an aspect, a ratio of the melt index of P_(s) to themelt index of P_(l) is less than about 3, alternatively less than about2, alternatively less than about 1.5, or alternatively less than about1.3. In another aspect, a ratio of the high load melt index of P_(s) tothe melt index of P_(l) is less than about 3, alternatively less thanabout 2, alternatively less than about 1.5, or alternatively less thanabout 1.3.

Conventional titanation of silica to produce a polymerization catalyst,herein termed standard organic titanation, involves the addition of atitanium compound such as titanium alkoxide (e.g., Ti(OiPr)₄), termedtitanium loading, in an organic solvent to preformed silica particles.The products of this process are heterogeneous silica particles having anon-uniform surface coating of titanium formed onto the underlyingsilica nanoparticles. Standard organic titanation results in a catalystthat is heterogeneous both in terms of particle size and in terms oftitanium loading.

Specifically, during standard organic titanation of silica, titanium isadded to a preformed silica particle. Each titanium atom reacts with thefirst silica atom it encounters and consequently, depending on theamount of titanium added, the titanium atoms react with silica at thesurface and can be exhausted before fully penetrating the interior ofthe silica particle. The result of this particular process is theformation of titanium-coated silica particles having a non-uniformcoating of titanium. This type of catalyst comprises compositionallydistinct particles that exhibit distinct types of catalytic behavior.Specifically, the catalyst has (a) a first behavior attributed to theouter portion of the particle coated with titanium and (b) a secondbehavior attributed to the inner portion of the particle having littleto no titanium. For example, the outer portion of the particle (havingsome titanium coating e.g., 8 wt. %) catalyzes the production of lowmolecular weight (MW) polymer that has the tendency to dissolve and issticky while the inner portion of the particle (having little to notitanium loading e.g., 0%) catalyzes the production of higher molecularweight polymer with the attendant undesirable rheological properties.

A catalyst prepared by standard organic titanation has behavior that isfurther complicated by the broad particle size distribution ofconventional silica supports. Conventional silica supports can haveparticles with diameters ranging from about 2 microns to greater thanabout 300 microns. This results in a third type of catalyst behaviorattributed to the particle size distribution of the pre-formed silicawhere due to variance in silica particle size, the chemical compositionof the particles vary. For example, with an average titanium loading of2.5%, particles on the lower end of the particle size distribution mayhave titanium present in amounts corresponding to 8.0% while particleson the higher end may experience titanium amounts of 0.5% or even less.The result is a plurality of particles of differing titanium amountscatalyzing the production of polymers that vary in features such as MWDand long and/or short chain branching. The relationship between featuresof the polymer produced (e.g., MWD, level of chain branching) and thestructural features of the catalyst produced by standard organictitanation of silica can be described as follows:

Polymer features α amount of titanium added+percentage titanium percatalyst particle

In other words the disclosed polymer features are proportional to theamount of titanium added and the percentage titanium per catalystparticle.

In an aspect, standard organic titanation of silica where the silica hasa broad particle size distribution exhibits an overall catalyticactivity, denoted E, attributable to a number of factors including (i)the catalytic activity of the outer layer of particles coated withtitanium, denoted z_(i) and (ii) the catalytic activity of the innerportion of particles with little to no titanium, denoted z_(ii).Further, the depth of the outer layer of particles coated with titaniumvaries depending on the particle size. This leads to yet another factor,related to the weight percent titanium on the silica which variesaccording to size denoted z_(iii). The result is an overall catalyticactivity Σ for the standard organic titanation of silica reflecting thecatalytic activity of a number of particle types; Σ=k_(i)+k_(ii)+k_(iii)or a multi-component catalytic activity.

In an aspect, HATCs of the present disclosure are characterized by thepresence of a plurality of titanium-silica nanoparticle agglomerateswherein the titanium-silica nanoparticles have a uniform amount oftitanium present per titanium silica nanoparticle. In an aspect, thetitanium-silica nanoparticles, having approximately the same particlesize, have about the same amount of titanium present per amount oftitanium loaded. In sharp contrast to the standard organic titanation ofsilica, HATCs may have a coefficient of variance of equal to or lessthan about 1, alternatively from about 0.1 to about 0.9 or alternativelyfrom about 0.2 to about 0.9 for the amount of titanium present pertitanium-silica nanoparticle. This unexpectedly beneficial narrowdistribution of titanium per titanium-silica nanoparticle results in amore homogenous catalyst than produced by standard organic titanation.

X-ray photoelectron spectroscopy (XPS), also known as electronspectroscopy for chemical analysis (ESCA), is a technique for analyzingthe surface chemistry of a material. XPS can measure the elementalcomposition, empirical formula, chemical state and electronic state ofthe elements within a material. XPS spectra are obtained by irradiatinga solid surface with a beam of X-rays while simultaneously measuring thekinetic energy of electrons that are emitted from the top 1 nm to 10 nmof the material being analyzed. A photoelectron spectrum is recorded bycounting ejected electrons over a range of electron kinetic energies.Peaks appear in the spectrum from atoms emitting electrons of aparticular characteristic energy. The energies and intensities of thephotoelectron peaks enable identification and quantification of allsurface elements (except hydrogen).

Small variations in binding energies of the photoelectron lines as wellas Auger lines, satellite peaks, and multiple splitting can be used toidentify chemical states. A schematic representations of the Augerprocess is shown in FIG. 4.

The Auger electrons are emitted with kinetic energies that are onlydependent on the electronic state of the element responsible for theejected electron. That is to say, unlike photoelectric lines, changingthe X-ray characteristic energy does not alter the position of the Augerlines in the recorded spectra with respect to a kinetic energy scale.

During XPS, one can obtain an idea of where the titanium atoms arelocated with respect to the silica atoms as the X-ray beam onlypenetrates the particle to a depth of about 20 Angstroms. The X-raysignal exponentially decays so that the surface of the particle ispreferentially excited resulting in a stronger signal from the surface.

In an aspect, the HATCs of this disclosure at 2.0 wt. % titanium loadingwhen subjected to XPS displays a ratio of the 2P signal oftitanium:silicon of equal to or less than about 0.04, alternativelyequal to or less than about 0.025 or alternatively equal to or less thanabout 0.02. As disclosed herein, the XPS values of HATCs indicate theuniformity of the titanium distribution throughout the titanium-silicananoparticle when compared with catalyst particles prepared by thestandard organic titanation of silica.

An SEM of a HATC of this disclosure indicates the presence of titaniumthroughout the particle at titanium loadings less than saturation level.In other words, unlike a catalyst produced by the standard organictitanation of silica, the HATCs have titanium atoms present when thesilica particles are formed resulting in the distribution of titaniumthroughout the titanium-silica nanoparticle. Further, thetitanium-silica nanoparticles of the HATCs are characterized by auniformity of particle size, as disclosed herein. The result of HATCs ofthe present disclosure having the aforementioned characteristics is theabsence of (i) an outer layer of particles coated with titanium and (ii)an inner portion of particles with little to no titanium. In otherwords, the HATCs display a level of uniformity that results in thecatalytic activity being attributable to catalytic particles having anarrow particle size distribution with titanium distributed throughoutthe entire particle. Consequently, the HATC has a catalytic activityreflective of a single particle type or Σ=k_(i) and the catalyticactivity approximates that of a uni-component catalyst.

EXAMPLES

The following examples are given as particular aspects of the disclosureand to demonstrate the practice and advantages thereof. It is understoodthat the examples are given by way of illustration and are not intendedto limit the specification or the claims to follow in any manner.

The melt index of a polymer resin represents the rate of flow of amolten resin through an orifice of 0.0825 inch diameter when subjectedto a force of 2,160 grams at 190° C. The MI values are determined inaccordance with ASTM D1238. Further, the high load melt index of apolymer resin represents the rate of flow of a molten resin through anorifice of 0.0825 inch diameter when subjected to a force of 21,600grams at 190° C. The HLMI values are determined in accordance with ASTMD1238 condition E.

A “Quantachrome Autosorb-6 Nitrogen Pore Size Distribution Instrument”was used to determine the surface area and pore volume of the supports.This instrument was acquired from the Quantachrome Corporation ofSyosset, N.Y. Particle size distribution was determined by lightscattering using a Leeds & Northrup Microtrac FRA instrument. A fewmilligrams of sample was introduced into a stream of circulating water.The particle size distribution was determined by volume weighting fromthe range of 0.1 to 1000 microns, using 100 channels, and assuming aspherical shape.

Polymerization runs were made in a 2.2 liter steel reactor equipped witha marine stirrer rotating at 400 rpm. The reactor was surrounded by asteel jacket containing boiling methanol with a connection to a steelcondenser. The boiling point of the methanol was controlled by varyingnitrogen pressure applied to the condenser and jacket, which permittedprecise temperature control to within half a degree centigrade, with thehelp of electronic control instruments.

Unless otherwise stated, a small amount (0.01 to 0.10 grams normally) ofthe solid catalyst was first charged under nitrogen to the dry reactor.Next 1.2 liters of isobutane liquid was charged and the reactor heatedup to the specified temperature, typically 105° C. unless statedotherwise. Finally ethylene was added to the reactor to equal a fixedpressure, normally 550 psig, which was maintained during the experiment.The stirring was allowed to continue for the specified time, usuallyaround one hour, and the activity was noted by recording the flow ofethylene into the reactor to maintain the set pressure.

After the allotted time, the ethylene flow was stopped and the reactorslowly depressurized and opened to recover a granular polymer powder. Inall cases the reactor was clean with no indication of any wall scale,coating or other forms of fouling. The polymer powder was then removedand weighed. Activity was specified as grams of polymer produced pergram of solid catalyst charged per hour.

A silica-titania-chromia hydrogel was made according to U.S. Pat. No.3,119,569 in which sodium silicate solution was added to an aqueoussolution of TiOSO₄ and Cr₂(SO₄)₃ in dilute sulfuric acid. The amounttitanyl sulfate present in the solution was enough to impart a final Ticontent in the finished catalyst of 2.5 wt. %. Likewise, the amount ofchromium sulfate in the solution was sufficient to produce a finishedcatalyst containing 1 wt. % chromium.

The pH of the acidic solution increased as sodium silicate was added,and the solution gelled at pH 6. A small amount of NH₄OH was added tobring the aging pH to 8, where it was held for 3 hours at 80° C.Afterward the gel was given a series of 7 wash treatments in water,which was drained off after each step. After all the excess water wasdrained away, the final hydrogel had silica content of 12 wt. % withmost of the remainder of the mass being water.

This hydrogel was then divided into three parts which were subsequentlydried by three different methods. In each case the resulting catalystwas finally calcined in dry air at 870° C. for three hours. Incomparative example 1 the hydrogel sample was simply dried in a vacuumoven at 100° C. for 18 hours. In comparative example 2, the hydrogelsample was spray-dried at about 120° C. In comparative example 3, thehydrogel sample was first boiled in butyl acetate to remove the water asan azeotrope, then the butyl acetate still in the pores of the gel wasdriven out by drying in a vacuum oven at 100° C. for 18 hours. Aftercalcination at 870° C. all three comparative catalysts were tested in alaboratory reactor at 109° C. as described above. The physicalproperties of these catalysts, and the polymerization results, are shownin Table 1 below.

In another common approach used to produce comparative example 4, acommercial catalyst was obtained from W.R. Grace under the trade name ofHA30W, having an average particle size of 100 microns, a chromiumcontent of 1 wt. %, no titanium, a pore volume of 1.6 mL/g, and asurface area of about 300 m²/g. This silica was dried at 200° C.overnight, and then slurried in heptane, to which was added titaniumtetraisopropoxide in an amount to render the catalyst 2.5 wt. %titanium. The heptane was then evaporated and the amount of carbon lefton the catalyst was determined by combustion analysis. Finally, thecatalyst was calcined at 870° C., during which an exotherm of 250° C.was observed starting at about 270° C. During the activation thecatalyst produced a significant amount of 1-olefin (specificallypropylene) HRVOC. This catalyst was also tested in laboratorypolymerization and the resultant data is again listed in Table 1 ascomparative example 4.

A series of catalysts of the type disclosed (HTACs 1-3) herein were thenmade following the same procedure described above to make a tergelledCr/silica-titania hydrogel. However, in these experiments, not as muchwater was added to dilute the sodium silicate solution. This resulted inmore concentrated alkaline silicate solutions to which the acidictitanyl sulfate solution was then added as noted above to causegelation. The resulting hydrogels made were also more concentrated, thatis, they contained a higher percentage of silica. The actual values arelisted in Table 1 below. Gelation also occurred at a lower pH because ofthe higher solids concentration, as described in “The Chemistry ofSilica, Solubility, Polymerization” by Ralph K. Ihler. Consequently, theresulting hydrogel of the present disclosures contained 25 wt. % silica,twice that of the comparative catalysts. Otherwise, the process wasrepeated exactly like that described for the comparative catalysts. Thephysical properties of the HATCs and the laboratory polymerizationresults obtained, are listed again in Table 1, where the twopreparations can be compared.

Notice that for each drying method, the HATCs produced a higher porevolume than the comparative catalyst. The is because the higher silicacontent in the hydrogel provides a more sturdy framework that can betterresist shrinkage during drying by the high surface tension of water inthe pores. This high pore volume is desirable because it in turnproduced a more active catalyst, and higher melt index polymer, both ofwhich favor higher production rates in a commercial polymerizationplant.

TABLE 1 Process Comparative Inventive Sample 1 2 3    4* 1 2 3 GelationpH 6 6 6   2 2 2 2 Aging pH 8 8 8  10 8 8 8 % Silica in gel 12% 12% 12%25% 25% 25% 25% Drying Vac. Spray Azeotroped Spray Vac. Spray Azeotropedmethod Oven Dried Dried Oven Dried Surface 400 460 450  450 420 440 470Area m2/g Pore Volume, 0.85 0.92 2.53     1.61 1.33 1.67 2.87 mL/gActivity, 2300 3600 5200 4650 3800 4900 5700 gPE/g/h Melt Index 0.831.21 5.35     4.32 3.21 4.87 7.42 1-Olefin 0 0 0.3% 1.6% 0.0% 0.0% 0.3%HRVOC, wt % % Carbon 0 0 0.8% 4.7% 0.0% 0.0% 0.7% after drying Exotherm,0 0 85° C. 340° C. 0 0 82° C. deg C. *Titanium added by organic surfacecoating, not cogellation

Example 2

100 micron particles were obtained from comparative sample 4 (seeTable 1) which were prepared by standard organic titanation to obtain acatalyst having 2.5 wt % Ti loading. After microtoming the particles inhalf, scanning electron micrographs (SEM) of these catalyst particleswere acquired, and are shown in FIG. 1A.

Referring to FIG. 1A, a SEM of a silica-titania particle is shown, cutin half. The average titanium loading in comparative sample 4, for allparticles, was 2.5 wt % Ti. Referring to FIG. 1A, the titanium, which isindicated by the lighter areas, is concentrated in the exterior skin ofthe 100 micron particle. The titanium concentration at the skin of theparticle was measured at 8.2 wt % titanium. In contrast, the titaniumloaded measured in the interior was 0.04 wt % titanium Thus, the ratioof Ti(outside)/Ti(center) is 8.2/0.04=205.

However, when the titanium loading was increased to 8 wt. % (i.e.,saturation level), the SEM demonstrates the presence of about 8 wt %titanium throughout the particle, FIG. 1B. Notably, a standard organictitanation with a titanium loading of 8%, however, has been demonstratedto catalyze the production of a polyethylene having commerciallyundesirable rheological properties, including smoke, poor color, poormelt strength, enhanced swelling and poor tear properties.

FIG. 2 is a comparison of the SEMs of two silica-titania particlesprepared by either standard organic titanation or using the methods ofthe present disclosure. First, a comparative catalyst, designatedcomparative sample 5, that was similar to comparative sample 4 with theexception that the catalyst had a titanium loading of 3.0 wt % Ti wasprepared. In FIG. 2, a 120 micron macroparticle of comparative sample 5was microtomed in half. The SEM pictures of this particle are shown inline 1 of FIG. 2. Notice that again, the titania is concentrated into anouter skin. The Ti loading in the skin was measured to be 7.93 wt % Ti,or near saturation. In contrast, the center of this particle containedonly 0.12 wt % Ti. Therefore the ratioTi(outside)/Ti(center)=7.93/0.12=66.1.

The other catalyst shown in FIG. 2 was made by the methods of thepresent disclosure (i.e., HATC) and was designated inventive sample 4.Inventive sample 4 was made to contain an average titanium loading amongall macro particles of 3.0 wt % Ti using the method described for thepreparation of inventive sample 2, see Table 2, with the exception ofthe amount of titanium loaded. A 115 micron particle of inventive sample4 was microtomed in half for SEM analysis, which is shown in line II ofFIG. 2. Notice that for inventive sample 4, the titanium is evenlydispersed throughout the particle. The outside of inventive sample 4measured 3.12% Ti and the center measured 3.06%, so that the ratio ofTi(outside)/Ti(center)=3.12/3.06=1.02.

Columns A and B of FIG. 2 shows that for both catalysts, images of themacroparticle as a whole (Column A), or imaged specifically for silica(Column B), appeared strikingly similar. In sharp contrast, when imagingspecifically for titanium, the catalyst prepared by standard organictitanation, FIG. 2 I-C, showed the titanium limited to the outer portionof the macro-particle while the HATC, FIG. 2 II-C has titaniumdistributed throughout the nanoparticle and consequently themacro-particle too.

Another measurement was then made on the catalysts from Example 1,comparative sample 5 and inventive sample 3. FIG. 3 shows the particlesize distributions obtained from light scattering of these twocatalysts. This is a particularly good comparison, because it is thedistribution of the catalysts of the present disclosure, in thisatypical case, that is the broader of the two, and would then beexpected to be the one which would be most likely to exhibitheterogeneity. However, this was not the case.

From the two particle size distributions in FIG. 3, one can estimatethat, for inventive catalyst 5, the larger 10% of particles (by weight)would be approximately that portion that remained on a 60 mesh Tylerscreen. And, using the same particle size distribution, it was observedthat the smaller 10% of these particles would be approximately theamount that passed through a 400 mesh screen. Similarly, usingcomparative catalyst 5 and the accompanying particle size distributionin FIG. 3, it was observed that the larger 10% particle size isapproximately that portion that stays on a 120 mesh screen, and thesmaller 10% particle size is that portion that passes through a 325 meshscreen. Therefore both of these catalysts were so screened, to obtainenough catalyst to measure the titania content of these fractions. Theresults are summarized in Table 2 below.

TABLE 2 Example Comp-4 Comp-5 Inv-4 Ti Method Surface Surface CogelAverage Ti wt % 2.5 3.0 3.0 Outside Ti wt % 8.2 7.93 3.12 Center Ti wt %0.04 0.12 3.06 Ratio 205 66.1 1.02 Smaller 10%, mesh thru 325 thru 400wt % Ti 6.21 2.95 Melt index 1.21 0.47 HLMI 83.2 42.2 Larger 10% on 120on 60 wt % Ti 1.32 3.03 Melt index 0.11 0.39 HLMI 14.9 37.6Ti(small)/Ti(large) 4.70 0.97 MI(small)/MI(large) 11.0 1.21HLMI(small)/HLMI(large) 5.6 1.12

It was observed that despite the atypical broader particle sizedistribution of the catalysts of the present disclosure, theheterogenity in the titanium composition for the catalysts of thepresent disclosure is much narrower than the comparative catalyst as afunction of particle size.

Once the four catalyst samples were obtained (i.e., comparative samples4 and 5 and inventive samples 3 and 4) they were then calcined in dryair for 3 hours at 650° C. The samples were then tested forpolymerization activity as described above. Each sample was found to beactive for ethylene polymerization. The melt index and HLMI of theresult polymers were measured, and are listed in Table 2. It wasobserved that both the MI and HLMI heterogeneity were higher for thecomparative catalyst.

ADDITIONAL DISCLOSURE—PART I

The following enumerated aspects of the present disclosures are providedas non-limiting examples.

A first aspect which is a method of preparing a catalyst supportcomprising contacting an acid-soluble titanium-containing compound withan acid to form a first mixture, contacting the first mixture with analkali metal silicate to form a hydrogel which has a silica content offrom about 18 wt. % to about 35 wt. % based on the total weight of thehydrogel, contacting the hydrogel with an alkaline solution to form anaged hydrogel, washing the aged hydrogel to form a washed hydrogel, anddrying the washed hydrogel to produce a titanium-containing-silicasupport wherein the support has a pore volume equal to or greater thanabout 1.4 cm³/g.

A second aspect which is a method of preparing a catalyst comprisingcontacting an acid-soluble titanium-containing compound with an acid toform a first mixture, contacting the first mixture with an alkali metalsilicate to form a hydrogel which has a silica content of from about 18wt. % to about 35 wt. % based on the total weight of the hydrogel,contacting the hydrogel with an alkaline solution to form an agedhydrogel, washing the aged hydrogel to form a washed hydrogel, anddrying the washed hydrogel to produce a titanium-containing-silicasupport, wherein a chromium compound is included in the method to form achrominated-titanium-containing silica, either through cogelation of thehydrogel in the presence of a chromium-containing compound or contactingthe titanium-containing-support with a chromium-containing compound andwherein the support has a pore volume equal to or greater than about 1.4cm³/g.

A third aspect which is a method of preparing a catalyst comprisingcontacting an acid-soluble titanium-containing compound with an acid toform a first mixture, contacting the first mixture with an alkali metalsilicate to form a hydrogel which has a silica content of from about 18wt. % to about 35 wt. % based on the total weight of the hydrogel,contacting the hydrogel with an alkaline solution to form an agedhydrogel, washing the aged hydrogel to form a washed hydrogel, dryingthe washed hydrogel to produce a titanium-containing-silica support, andimpregnating the titanium-containing-support with a chromium-containingcompound to form a chrominated-titanium-containing silica wherein thesupport has a pore volume equal to or greater than about 1.4 cm³/g.

A fourth aspect which is a method of preparing a catalyst comprisingcontacting an acid-soluble titanium-containing compound with an acid toform a first mixture, contacting the first mixture with an alkali metalsilicate to form a hydrogel which has a silica content of from about 18wt. % to about 35 wt. % based on the total weight of the hydrogel,contacting the hydrogel with an alkaline solution to form an agedhydrogel, washing the aged hydrogel to form a washed hydrogel, and spraydrying the washed hydrogel in the presence of a chromium-containingcompound to produce a chrominated-titanium-containing silica wherein thesupport has a pore volume equal to or greater than about 1.4 cm³/g.

A fifth aspect which is a method of preparing a catalyst comprisingcontacting an acid-soluble titanium-containing compound and achromium-containing compound with an acid to form a first mixture,contacting the first mixture with an alkali metal silicate to form ahydrogel which has a silica content of from about 18 wt. % to about 35wt. % based on the total weight of the hydrogel, contacting the hydrogelwith an alkaline solution to form an aged hydrogel, washing the agedhydrogel to form a washed hydrogel, and drying the washed hydrogel toform a chrominated-titanium-containing silica wherein the support has apore volume equal to or greater than about 1.4 cm³/g.

A sixth aspect which is the method of any of the first through fifthaspects wherein the contacting the first mixture with an alkali metalsilicate to form a hydrogel is continuous.

A seventh aspect which is the method of any of the first through sixthaspects wherein the contacting the first mixture with an alkali metalsilicate to form a hydrogel occurs at a pH of less than about 4.

An eighth aspect which is the method of any of the second through fifthaspects further comprising calcination of thechrominated-titanium-containing silica at a temperature of from about400° C. to about 1,000° C. to form a polymerization catalyst.

A ninth aspect which is the method of the eighth aspect wherein thepolymerization catalyst has a surface area of from about 400 m²/g toabout 1000 m²/g.

A tenth aspect which is the method of any of the eighth through ninthaspects wherein the polymerization catalyst has pore volume equal to orgreater than about 1.7 cm³/g.

An eleventh aspect which is the method of any of the first through tenthaspects wherein the acid-soluble titanium-containing compound comprisestrivalent titanium, tetravalent titanium, titania, or combinationsthereof.

A twelfth aspect which is the method of the eleventh aspect wherein thetetravalent titanium comprises TiCl₄, TiOSO₄, TiBr₄, TiOCl₂, TiOBr₂,TiO₂, TiO(oxylate)₂, or combinations thereof.

A thirteenth aspect which is the method of the eleventh aspect whereinthe trivalent titanium comprises Ti₂(SO₄)₃, Ti(OAc)₃, Ti(oxylate)₃,Ti(NO₃)₃, or combinations thereof.

A fourteenth aspect which is the method of any of the second throughthirteenth aspects wherein the chromium-containing compound compriseschromium trioxide, chromium acetate, chromium nitrate, chromium sulfate,tertiary butyl chromate, a diarene chromium (0) compound,biscyclopentadienyl chromium (II), chromium (III) acetylacetonate, orcombinations thereof.

A fifteenth aspect which is the method of any of the eighth throughtenth aspects wherein the chromium is present in an amount of from about0.01 wt. % to about 10 wt. % based on the total weight of thepolymerization catalyst.

A sixteenth aspect which is the method of any of the eighth throughtenth and the fifteenth aspects wherein the titanium is present in anamount of from 0.1 wt. % to about 10 wt. % based on the total weight ofthe polymerization catalyst.

A seventeenth aspect which is the method of any of the first throughsixteenth aspects wherein the alkali metal silicate comprises sodiumsilicate.

An eighteenth aspect which is the method of any of the first throughseventeenth aspects wherein the acid comprises a mineral acid.

A nineteenth aspect which is the method of any of the first througheighteenth aspects wherein the alkaline solution comprises sodiumhydroxide, ammonium hydroxide, sodium metasilicate, tetra-alkyl ammoniumhydroxide, potassium hydroxide or combinations thereof.

A twentieth aspect which is the method of any of the first throughnineteenth aspects wherein contacting with an alkaline solution occursfor a time period of from about 1 hour to about 24 hours.

A twenty-first aspect which is the method of any of the first throughtwentieth aspects wherein the washed hydrogel has an alkali metalpresent in an amount of less of than about 0.5 wt. % based on the totalweight of washed hydrogel.

A twenty-second aspect which is the method of any of the first throughtwenty-first aspects wherein the washed hydrogel is dried by spraydrying, flash drying, or oven drying.

A twenty-third aspect which is the method of any of the first throughtwenty-second aspects wherein an emission of a highly-reactive volatileorganic compound during calcination is an amount of from about 0 wt. %to about 0.5 wt. % based on the weight of the silica.

A twenty-fourth aspect which is the method of any of the first throughtwenty-third aspects wherein post-drying the support comprises less thanabout 0.3 wt. % carbon.

A twenty-fifth aspect which is the method of any of the first throughtwenty-fourth aspects wherein the exotherm during calcination of thecatalyst is less than about 100° C.

A twenty-sixth aspect which is the method according to any of the firstthrough fifth aspects wherein the contacting the first mixture with analkali metal silicate to form a hydrogel occurs at a pH of less thanabout 4 and further comprising calcination of thechrominated-titanium-containing silica at a temperature of from about400° C. to about 1,000° C. to form a polymerization catalyst, where thepore volume of the catalyst is greater than an otherwise similarcomparative catalyst prepared by contacting the first mixture with analkali metal silicate to form a comparative hydrogel at a pH of greaterthan about 4 and wherein the comparative hydrogel has a silica contentof less than about 18 wt. % based on the total weigh of the comparativehydrogel.

A twenty-seventh aspect which is the method according to any of thefirst through fifth aspects wherein the contacting the first mixturewith an alkali metal silicate to form a hydrogel occurs at a pH of lessthan about 4 and further comprising calcination of thechrominated-titanium-containing silica at a temperature of from about400° C. to about 1,000° C. to form a polymerization catalyst, where theactivity of the catalyst is greater than an otherwise similarcomparative catalyst prepared by contacting the first mixture with analkali metal silicate to form a comparative hydrogel at a pH of greaterthan about 4 and wherein the comparative hydrogel has a silica contentof less than about 18 wt. % based on the total weigh of the comparativehydrogel.

A twenty-eighth aspect which is an ethylene polymer prepared bycontacting the catalyst of any of the eighth through tenth aspects withethylene and an optional comonomer under conditions suitable for theformation of the ethylene polymer.

ADDITIONAL DISCLOSURE—PART II

The following enumerated aspects of the present disclosures are providedas non-limiting examples.

A first aspect which is a hydrogel comprising water, and a plurality oftitanium-silica nanoparticle agglomerates, wherein each titanium-silicananoparticle agglomerate is an agglomeration of titanium-silicananoparticles, the agglomerates having an average titanium loadingdesignated x with a coefficient of variation for the average titaniumloading of less than about 1.0, wherein a silica content of the hydrogelis of from about 10 wt. % to about 35 wt. % based on a total weight ofthe hydrogel.

A second aspect which is the hydrogel of the first aspect wherein thetitanium-silica nanoparticles have a coefficient of variation of theaverage titanium penetration depth of from about 0.1 to about 0.9.

A third aspect which is the hydrogel of any of the first through thesecond aspects wherein the titanium-silica nanoparticles have an averageparticle size of from about 4 to about 7 nanometers.

A fourth aspect which is the hydrogel of the third aspect wherein acoefficient of variation for the average particle size of thetitanium-silica nanoparticles is less than about 1.

A fifth aspect which is the hydrogel of any of the first through thefourth aspects having an x value of from about 0.25 wt. % to about 8 wt.% based on the total weight of the hydrogel.

A sixth aspect which is the hydrogel of any of the first through thefifth aspects having an x value of from about 1 titanium atoms/sqnm toless than about 4 titanium atoms/sqnm.

A seventh aspect which is the hydrogel of any of the first through thesixth aspects having a mL pore water in the pores of the hydrogel, per gof silica of from about 1.9 cm³/g to about 4.6 cm³/g.

An eighth aspect which is a xerogel prepared by dehydration of thehydrogel of any of the first through the seventh aspects.

A ninth aspect which is a pre-catalyst prepared by adding achromium-containing compound to the xerogel of the eighth aspect.

A tenth aspect which is a polymerization catalyst prepared by calciningthe pre-catalyst of the ninth aspect.

An eleventh aspect which is the polymerization catalyst of the tenthaspect having a macroparticle size distribution of from about 0.1 μm toabout 400 μm.

A twelfth aspect which is the polymerization catalyst of any of thetenth through the eleventh aspects having a S_(s):S_(l) ratio of about1.

A thirteenth aspect which is the polymerization catalyst of any of thetenth through the twelfth aspects having a Ti_(o)/Ti_(c) ratio of about1.

A fourteenth aspect which is the pre-catalyst of the ninth aspect havinga ratio of titanium X-ray photoelectron spectroscopy 2P signal tosilicon X-ray photoelectron spectroscopy 2P signal of equal to or lessthan about 0.04.

A fifteenth aspect which is the pre-catalyst of the ninth aspect havinga ratio of titanium X-ray photoelectron spectroscopy 2P signal tosilicon X-ray photoelectron spectroscopy 2P signal of equal to or lessthan about 0.025.

A sixteenth aspect which is the polymerization catalyst of the tenthaspect having a ratio of titanium X-ray photoelectron spectroscopy 2Psignal to silicon X-ray photoelectron spectroscopy 2P signal of equal toor less than about 0.025.

A seventeenth aspect which is the polymerization catalyst of the tenthaspect having a ratio of titanium X-ray photoelectron spectroscopy 2Psignal to silicon X-ray photoelectron spectroscopy 2P signal of equal toor less than about 0.04.

An eighteenth aspect which is a polyethylene polymer powder preparedusing the polymerization catalyst of the tenth aspect.

A nineteenth aspect which is the polyethylene polymer powder of theeighteenth aspect having a melt index ranging from about 0.01 g/10 minto about 100 g/10 min.

A twentieth aspect which is the polyethylene polymer powder of theeighteenth aspect having a high load melt index ranging from about 1g/10 min. to about 1000 g/10 min.

A twenty-first aspect which is the polyethylene polymer powder of theeighteenth aspect having a ratio of HLMI:MI of from about 30 g/10 min toabout 500 g/10 min.

While various aspects have been shown and described, modificationsthereof can be made by one skilled in the art without departing from thespirit and teachings of the invention. The aspects described herein areexemplary only, and are not intended to be limiting. Many variations andmodifications of the invention disclosed herein are possible and arewithin the scope of the invention. Where numerical ranges or limitationsare expressly stated, such express ranges or limitations should beunderstood to include iterative ranges or limitations of like magnitudefalling within the expressly stated ranges or limitations (e.g., fromabout 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes0.11, 0.12, 0.13, etc.). Use of the term “optionally” with respect toany element of a claim is intended to mean that the subject element isrequired, or alternatively, is not required. Both alternatives areintended to be within the scope of the claim. Use of broader terms suchas comprises, includes, having, etc. should be understood to providesupport for narrower terms such as consisting of, consisting essentiallyof, comprised substantially of, etc.

Accordingly, the scope of protection is not limited by the descriptionset out above but is only limited by the claims which follow, that scopeincluding all equivalents of the subject matter of the claims. Each andevery claim is incorporated into the specification as an aspect of thepresent invention. Thus, the claims are a further description and are anaddition to the aspects of the present disclosure. The discussion of areference in the disclosure is not an admission that it is prior art tothe present disclosure, especially any reference that may have apublication date after the priority date of this application. Thedisclosures of all patents, patent applications, and publications citedherein are hereby incorporated by reference, to the extent that theyprovide exemplary, procedural or other details supplementary to thoseset forth herein.

What is claimed is:
 1. A hydrogel comprising: water; and a plurality oftitanium-silica nanoparticle agglomerates, wherein each titanium-silicananoparticle agglomerate is an agglomeration of titanium-silicananoparticles, the agglomerates having an average titanium loadingdesignated x with a coefficient of variation for the average titaniumloading of less than about 1.0, wherein a silica content of the hydrogelis in a range of from about 18 wt. % to about 35 wt. % based on a totalweight of the hydrogel.
 2. The hydrogel of claim 1 wherein thetitanium-silica nanoparticles have a coefficient of variation of theaverage titanium penetration depth of from about 0.1 to about 0.9. 3.The hydrogel of claim 1 wherein the titanium-silica nanoparticles havean average particle size of from about 4 to about 7 nanometers.
 4. Thehydrogel of claim 3 wherein a coefficient of variation for the averageparticle size of the titanium-silica nanoparticles is less than about 1.5. The hydrogel of claim 1 having an x value of from about 0.25 wt. % toabout 8 wt. % based on the total weight of the hydrogel.
 6. The hydrogelof claim 1 having an x value of from about 1 titanium atoms/sqnm to lessthan about 4 titanium atoms/sqnm.
 7. The hydrogel of claim 1 having a mLpore water in the pores of the hydrogel, per g of silica of from about1.9 cm³/g to about 4.6 cm³/g.
 8. The hydrogel of claim 1 wherein thetitanium-silica nanoparticle agglomerates are formed from an acidictitanium solution comprising a trivalent titanium, tetravalent titanium,titania, or a combination thereof.
 9. The hydrogel of claim 8 whereinthe acidic titanium solution comprises TiCl₄, TiOSO₄, TiBr₄, TiOCl₂,TiOBr₂, TiO₂, TiO(oxylate)₂, or a combination thereof.
 10. The hydrogelof claim 8 wherein the acidic titanium solution comprises Ti₂(SO₄)₃,Ti(OAc)₃, Ti(oxylate)₃, Ti(NO₃)₃, or a combination thereof.
 11. Thehydrogel of claim 8 wherein the acidic titanium solution compriseshydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid,phosphoric acid, perchloric acid, sulfamic acid, or a combinationthereof.
 12. The hydrogel of claim 1 wherein titanium is present in anamount from about 0.01 wt. % to about 10 wt. % titanium based on thetotal weight of the hydrogel.
 13. The hydrogel of claim 1 furthercomprising a chromium-containing compound.
 14. The hydrogel of claim 13wherein the chromium-containing compound comprises a water-solublechromium compound, a hydrocarbon-soluble chromium compound, a chromium(II) compound, a chromium (III) compound, or a combination thereof. 15.The hydrogel of claim 13 wherein the chromium-containing compoundcomprises chromium carboxylates, chromium naphthenates, chromiumhalides, chromium pyrrolides, chromium benzoates, chromium dionates,chromium nitrates, chromium sulfates, or a combination thereof.
 16. Thehydrogel of claim 13 wherein the chromium-containing compound compriseschromium (III) isooctanoate, chromium (III)2,2,6,6-tetramethylheptanedionate, chromium (III) naphthenate, chromium(III) chloride, chromium (III) tris(2-ethylhexanoate), chromic fluoride,chromium (III) oxy-2-ethylhexanoate, chromium (III)dichloroethylhexanoate, chromium (III) acetylacetonate, chromium (III)acetate, chromium (III) butyrate, chromium (III) neopentanoate, chromium(III) laurate, chromium (III) sulfate, chromium (III) oxalate, chromium(III) benzoate, chromium (III) pyrrolide(s), chromium (III) perchlorate,chromium (III) chlorate, or a combination thereof.
 17. The hydrogel ofclaim 13 wherein the chromium-containing compound comprises chromousfluoride, chromous chloride, chromous bromide, chromous iodide, chromium(II) bis(2-ethylhexanoate), chromium (II) acetate, chromium (II)butyrate, chromium (II) neopentanoate, chromium (II) laurate, chromium(II) stearate, chromium (II) oxalate, chromium (II) benzoate, chromium(II) pyrrolide(s), chromous sulfate, or a combination thereof.
 18. Thehydrogel of claim 13 wherein the chromium-containing compound comprisestertiary butyl chromate in a hydrocarbon liquid; chromium trioxide inwater; chromium acetate in water; chromium nitrate in alcohol;zerovalent organochromium; or a combination thereof.
 19. The hydrogel ofclaim 13 wherein chromium is present in an amount of about 0.01 wt. % toabout 10 wt. % based on the total weight of the hydrogel.
 20. A xerogelprepared by dehydration of the hydrogel of claim 13.